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    <script>
        //双重for循环 语法结构
        //外层循环执行一次,里面的循环执行全部
        //代码验证
        for (var i = 1; i <= 3; i++) {
            console.log('这是外层循环第' + i + '次');
            for (var j = 1; j <= 3; i++) {
                console.log('这是外层循环第' + j + '次');

            }
        }
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